Rate of Oxidation of Liquid Iron by Pure Oxygen Shiro BAN-YA and Jae-Dong SHIM Synopsis: The rate of oxidation of liquid iron by oxygen gas has been s

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1 Rate of Oxidation of Liquid Iron by Pure Oxygen Shiro BAN-YA and Jae-Dong SHIM Synopsis: The rate of oxidation of liquid iron by oxygen gas has been studied using a volume constant technique. The process of oxidation consists of two stages of very rapid oxidation in the early stage and relatively slow oxidation in the second stage after the formation of iron oxide covering the surface of melt. The rate of the dissolution of oxygen into the melt was studied under the presence of three phases of gas, liquid oxide, and liquid iron to make clear the mechanism of oxidation. From the experimental results obtained, it was considered that the rate-determining step under the coexistence of three phases was the transport of solute gas through the stagnant layer in the oxide phase at the gas-oxide interface. This mechanism is supported by the following experimental facts: a) The rate of oxidation is proportional to the square root of oxygen pressure in the gas phase. b) The reaction rate decreases with decreasing the stirring of the melt. c) The rate is not influencedby the amount of oxygen and sulphur in liquid iron. The apprarent activation energy of the reaction is low, giving a value of 5 kcal/mol.

2 Fig. 1. Experimental apparatus. Fig. 2. Reaction chamber of apparatus.

3 Fig. 3. An example of variation of oxygen pressure in reaction bulb for oxidation process. Fig. 4. Rate of oxidation in the presence of oxide phase covering the melt. ( 1 )

4 ( 2 ) ( 3 ) (4 ) (5) (6) (7) (8) (9) (10) (11) (12)

5 (13) (14) Fig. 5. Correlation of experimental results on the basis of chemical reaction model at the gas/oxide interface. Fig. 7. Correlation of experimental results on the basis of parabolic oxidation model. Fig. 6. Correlation of experimental results on the basis of mass transport model through the oxide phase boundary layer adjacent to gas/oxide interface. Fig. 8. Differential plot of Experimental results for oxidation rate.

6 Table 1. Values of apparent rate constants, km, obtained on the basis of the model of mass transport through the oxide phase boundary layer adjacent to the gas/ oxide interface at 1600 Ž. Fig. 9. Effect of surface area on the apparent rate constant km at Ž. Fig. 10. Effect of initial oxygen pressure in gas storage bulb on oxidation rate at Ž.

7 Fig. 11. Effect of induction stirring of the melt on the apparent rate constant at Ž. Table 2. Effect of the induction stirring of the melt on the apparent rate constant. Fig. 12. Effect of oxygen content in Fe-0 melt on the apparent rate constant at Ž.

8 Fig. 13. Effect of sulfur content in Fe-S melt on the apparent rate constant at Ž. ( 18) Fig. 14. Arrhenius plot for temperature dependence of the apparent rate constant. (19)

9 1) P. A. DISTIN and S. G. WHITE: Can. Met. Quart., 9 (1970), p ) L. A. GREENBERG and A. MCLEAN: Trans. ISIJ, 14 (1974), p ) S. K. VIG and W.-K. Lu: JISI, 209 (1971), p ) T. CHOH, M. KURATA, and M. INOUYE: Proc. Int. Conf. Science and Tech. of Iron and Steelmaking, Tokyo, (1971), p ) T. EMI, W. M. BOOSTEIN, and R. D. PEHLKE: Met. Trans., 9 (1974), p ) P. KOFSTAD: High-Temperature Oxidation of Metals, (1966), p. 244 [N. Y., wiley] 9 ) W. D. KINGERY: J. Phys. Chem., 62 (1958), p ) W. M. BOOSTEIN and R. D. PEHLKE: Trans. Met. Soc. AIME, 245 (1969), p ) R. D. PEHLKE and J. F. ELLIOTT: Trans. Met. Soc. AIME, 227 (1963), p. 814

Fig. 1 Flow diagram of experimental apparatus employed Fig. 2 Porosity change during sulfurization of reduced sample pellets

Fig. 1 Flow diagram of experimental apparatus employed Fig. 2 Porosity change during sulfurization of reduced sample pellets Fig. 4 Simultaneous reduction-sulfurization and direct sulfurization of iron